Polymer composition, molded part and processes for production thereof

Abstract

The present invention relates to a polymer composition, consisting of (A) 30-90 wt. % of at least one thermoplastic polymer comprising at least a semi-crystalline semi-aromatic polyamide (SSPA-1) in an amount in the range of 30-90 wt. %; (B) 10-70 wt. % of at least one reinforcing agent, and (C) 0-25 wt. % of one or more other components; wherein the SSPA-1 consists of (A-1-a) 90-100 wt. % of repeat units derived from (i) an aromatic dicarboxylic acid and (ii) diamines, and (A-1-b) 0-10 wt. % of repeat units derived from other monomers; the diamines (ii) consist of 80-95 mole % of a linear aliphatic diamine, 5-20 mole % of 2-methyl-pentamethylene diamine, and 0-10 mole % of other diamines; and the SSPA-1 has a melting temperature (Tm) of at least 300 C. The invention further relates to a molded part made of the composition, a process for making the composition and a process for making the molded part.

Claims

1. A reinforced thermoplastic polymer composition consisting of: (A) a polymer comprising 30-90 wt. %, based on total weight of the polymer (A), of at least a first semi-crystalline semi-aromatic polyamide (SSPA-1) having a melting temperature (Tm) of at least 300 C.; (B) 10-70 wt. % of at least one reinforcing agent, and (C) 0-25 wt. % of one or more other components, wherein the SSPA-1 consists of: (A-1-a) 90-100 mole % of repeat units derived from (i) aromatic dicarboxylic acid and (ii) diamines, and (A-1-b) 0-10 mole % of repeat units derived from other monomers; wherein the diamines (ii) consist of 80-95 mole % of linear aliphatic diamine, 5-20 mole % of 2-methyl-pentamethylene diamine, and 0-10 mole % of other diamines; and wherein the mole percentages (mole %) of the linear aliphatic diamine, the 2-methyl-pentamethylene diamine and the other diamines are relative to the total molar amount of the diamines (ii); the mole % of (A-1-a) and (A-1-b) are relative to the total molar amount of monomeric repeat units (A-1-a) and (A1-b) in the SSPA-1; the weight percentages (wt. %) of the components (A), (B) and (C) are relative to the total weight of the composition, with the sum of the components (A), (B) and (C) being 100 wt. %.

2. The polymer composition according to claim 1, wherein the SSPA-1 has a melting temperature in the range of 310-350 C.

3. The polymer composition according to claim 2, wherein the aromatic dicarboxylic acid is terephthalic acid.

4. The polymer composition according to claim 1, wherein the aromatic dicarboxylic acid is selected from the group consisting of terephthalic acid, 2,6-naphthalene dicarboxylic acid, 4,4-biphenyl dicarboxylic acid and combinations thereof.

5. The polymer composition according to claim 1, wherein the diamines (ii) consist of 5-15 mole % of 2-methyl-pentamethylene diamine, 85-95 mole % of a linear aliphatic diamine, and 0-5 mole % of other diamines.

6. The polymer composition according to claim 1, wherein the linear diamines comprise 40-95 mole % of a C2-C8 diamine, relative to the total molar amount of the linear diamines (ii).

7. The polymer composition according to claim 1, wherein the component (B) comprises inorganic fibers and/or inorganic fillers.

8. The polymer composition according to claim 1, wherein the component (B) comprises glass fibers and/or carbon fibers.

9. The polymer composition according to claim 1, wherein the component (B) is present in an amount in the range of 30-50 wt. %, relative to the total weight of the composition.

10. The polymer composition according to claim 1, wherein the linear diamines comprise 60-95 mole % of a C2-C6 diamine, relative to the total molar amount of the linear diamines (ii).

11. A process for preparing a polymer composition according to claim 1, comprising melt-mixing the components (A), (B) and (C).

12. A molded part comprising an element made of the polymer composition according to claim 1.

13. The molded part according to claim 12, wherein the molded part is an automotive part or a part of an electronic device.

14. The molded part according to claim 12, wherein the element is made in a mold with a multi-gate cavity.

15. A process for making a molded part which comprises injection molding the polymer composition according to claim 1 into a mold.

16. The process according to claim 15, wherein the mold comprises a multi-gate cavity.

Description

(1) The invention is further illustrated with the following non-limiting examples and comparative experiments.

(2) Materials

(3) PA-1 PA-6T/DT (60/40 molar ratio): Zytel HTN51G45HSL, glass fiber reinforced grade (commercially available from DuPont) PA-2 PA-6T/4T copolymer (65/35 molar ratio) (made by DSM) PA-3 PA-6T/4T/DT copolymer (58/32/10 molar ratio) (made by DSM)

(4) Herein the polyamides consist of repeat units derived from respectively: 1,6-hexanediamine and terephthalic acid (abbreviated as 6T), 1,4-butanediamine and terephthalic acid (abbreviated as 4T), and 2-methyl-pentamethylene diamine and terephthalic acid (abbreviated as DT).

(5) Compounding

(6) Polyamide compositions were prepared on a twin screw extruder, employing standard molding conditions. For the compositions of Examples I-Ill and Comparative Experiments A and B, the temperature of the extruded melt was typically about 350-360 C. For Comparative Experiment C the melt temperature was about 330 C. After the melt compounding the resulting melt was extruded into strands, cooled and cut into granules.

(7) Injection MoldingPreparation of Test Bars for Mechanical Testing

(8) Dried granulate material was injection molded into a mold to form test bars conforming ISO 527 type 1A; the thickness of the test bars was 4 mm. The polyamide compositions were injection molded into appropriate test molds using a standard injection molding machine. Test bars were prepared using either a single gated mold for standard test bars or a double gated mold for production of test bars with a weld line, each gate located at an opposite end of the sample and causing the formation of a weld line, while applying the same conditions as for the standard test bars. The setting temperature of the T-melt in the injection molding machine was about 330 C. for PA-1 and 350 C. for PA-2 and PA-3; the temperature of the mold was 140 C.

(9) Testing

(10) Melting temperature (Tm)

(11) The measurements of the melting temperature (Tm) were carried out with a Mettler Toledo Star System (DSC) using a heating and cooling rate of 10 C./min. in an N2 atmosphere. For the measurements a sample of about 5 mg pre-dried powdered polymer was used. The pre-drying was carried out at high vacuum, i.e. less than 50 mbar and a 130 C. during 16 hrs. The sample was heated from 0 C. to a temperature about 30 C. above the melting temperature at 10 C./min, immediately cooled to 0 C. at 10 C./min and subsequently heated to about 30 C. above the melting temperature again at 10 C./min. For the melting temperature Tm the peak value of the melting peak in the second heating cycle was determined, according to the method of ISO-11357-1/3, 2011.

(12) Tensile Strength

(13) The tensile strength was measured in a tensile test according to ISO 527/1 at 150 C., at a drawing speed of 5 mm/min.

(14) Weldline Strength

(15) The weldline strength was measured in a tensile test according to ISO 527/1 at 23 C., at a drawing speed of 5 mm/min.

(16) The compositions and test results have been summarized in Table 1.

(17) TABLE-US-00001 TABLE 1 Compositions and properties of Examples I-III and Comparative Experiments (A-C) CE-A EX-I CE-B EX-II CE-C EX-III Composition (wt.%) PA-6T/4T (65/35) 59.2 54.6 PA-6T/4T/DT (58/32/10) 59.5 54.6 49.5 PA-6T/DT (60/40) 54.5 Glass fibers 40 40 45 45 45 50 Additive package 0.8 0.5 0.4 0.4 0.5 0.5 (ST + MRA) Properties Tm ( C.) 342 337 342 337 300 337 Tensile strength 135 134.4 140 136 83 138 at 150 C. [MPa] Weldline strength 59.4 73.4 70 78 69 81 at 23 C. [MPa]

(18) The results show an increased weldline strength for the compositions according to the invention, compared to corresponding compositions not comprising 2-methyl-pentamethylene diamine terephthalamide units, while the tensile strength at high temperature remains at a high level. This result is highly surprising and in contrast with the known composition comprising a larger amount of 2-methyl-pentamethylene diamine terephthalamide units, which shows a lower weldline strength and a significant drop in tensile strength at high temperature.